The sum of three numbers is 9. The second is 7 less than the first. The third is 1 more than three times the first. Find the numbers.

Solution:

First number = x

second number = x - 7

third number = 3x + 1

x + x - 7 + 3x + 1 = 9

5x = 15

 x = 15/5 = 3

second number = x - 7 = 3 - 7 = -4

third number = 3x + 1 = 10